The present invention relates to the field of semiconductor package with mixed copper pillar or bump pad sizes.
In order to ensure miniaturization and multi-functionality of electronic products or communication devices, semiconductor packages are required to be of small in size, multi-pin connection, high speed, and high functionality. Increased Input-Output (I/O) pin count combined with increased demands for high performance ICs has led to the development of flip chip packages.
Flip-chip technology typically uses solder bumps on chip to interconnect the package media such as package substrate. The flip-chip is bonded face down to the package substrate through the shortest path. These technologies can be applied not only to single-chip packaging, but also to higher or integrated levels of packaging in which the packages are larger and to more sophisticated substrates that accommodate several chips to form larger functional units. The flip-chip technique, using an area array, has the advantage of achieving the higher density of interconnection to the device and a very low inductance interconnection to the package.
Recently, copper pillar bump technology has been proposed. Instead of using a solder bump, the electronic component is connected to a substrate by means of a copper pillar bump, which achieves finer pitch with minimum probability of bump bridging, reduces the capacitance load for the circuits, and allows the electronic component to perform at higher frequencies.
Conventional flip-chip package utilizing copper pillar bump is implemented with a single copper pillar size. For example, to meet huge amount of die-to-die connections, a smaller copper pillar size is used. However, this makes the high-speed or power-consuming IP fail to meet the electrical constraints. On the other hand, when a larger size of the copper pillar is used, the die size greatly increases.